LCDs are generally categorized by their driving modes into active matrix LCDs and passive matrix LCDs. Compared with passive matrix LCDs, active matrix LCDs generally have faster response speeds, better color displays, and higher contrast ratios. For these reasons, active matrix LCDs are more popular than passive matrix LCDs.
Active matrix LCDs are usually categorized, according to the manner in which they transport light, into reflective mode, transmissive mode, and transflective mode active matrix LCDs. Though reflective mode, transmissive mode, and transflective mode active matrix LCDs adopt different modes of transporting light, they all use thin film transistors (TFTs) to achieve an active display.
In general, a TFT LCD includes a TFT substrate. A typical TFT substrate mainly includes a plurality of gate lines arranged in parallel and extending along a first direction, and a plurality of data lines arranged in parallel and extending along a second direction perpendicular to that of the gate lines. Thus, the gate lines and data lines define a multiplicity of pixel regions arranged in an array.
FIG. 4 is a schematic, top cross-sectional view of a configuration of components of a pixel region of a typical TFT substrate. FIG. 5 is a schematic, side cross-sectional view corresponding to part of line V-V of FIG. 4. A pixel region 1 of a TFT substrate 10 is defined by two parallel gate lines 12, and a data line 11 perpendicularly crossing the data lines 12. The pixel region 1 includes a pixel electrode 13, a TFT 16, and a plurality of storage electrode elements 14 therein. The storage electrode elements 14 extend from the gate line 12, are stripe-shaped, and are parallel to each other. The storage electrode elements 14 cooperatively form a lower storage electrode. The pixel electrode 13 partially overlaps the storage electrode elements 14. Regions of the pixel electrode 13 that overlap the storage electrode elements 14 are cooperatively used as an upper storage electrode. The upper and lower storage electrodes and an intervening dielectric layer 17 cooperatively form a storage capacitor.
In operation, column data drivers (not shown) simultaneously apply the required voltages to every pixel in a row as selected by a row scan driver (not shown). The scan driver turns the TFTs 16 on, to charge the storage capacitors of every pixel region 1 in that row. Once each TFT 16 is turned off, the storage capacitor holds the pixel region 1 at the set voltage level until the next refresh cycle.
However, the storage electrode elements 14 extend from and electrically connect to the gate line 12, which increases the load of the gate line 12 when it is being used to hold the pixel region 1 at the set voltage level. This means that the LCD employing the TFT substrate 10 has high power consumption.
What is needed, therefore, is an LCD having a TFT substrate with a low consumption storage capacitor.